1. Field of the Invention
The present invention relates to a manufacturing method of an SOI (silicon on insulator) substrate having a semiconductor layer formed of silicon or the like and a method for manufacturing a semiconductor device by using the SOI substrate.
Note that the ‘semiconductor device’ in this specification refers to a device in general that can operate by utilizing semiconductor characteristics, and an electro-optical device, an integrated circuit, and an electronic device are all included in the category of the semiconductor device.
2. Description of the Related Art
Integrated circuits using an SOI substrate in which a thin single-crystal silicon layer is formed over an insulating layer have been developed. By utilizing characteristics of the thin single-crystal silicon layer, transistors in the integrated circuit can be formed so as to be completely isolated electrically for each element, and the transistors can be formed to be a full depletion type, so that a semiconductor integrated circuit with high added value such as high integration, high speed driving, and low power consumption can be realized.
As a method for manufacturing an SOI substrate, a bonding method in which a hydrogen ion implantation step and a separation process are combined with each other is known. In this method, an SOI substrate is manufactured mainly by the following process: hydrogen ions are implanted into a silicon wafer to form a damaged region at a predetermined depth from the surface; a silicon wafer which is to be a base substrate is oxidized so that a silicon oxide film is formed; the silicon wafer into which the hydrogen ions are implanted is bonded to the silicon wafer where the silicon oxide film is formed, whereby the two silicon wafers are attached to each other; heat treatment is performed thereon so that the bonded wafer is cleaved in the damaged region; and heat treatment is performed to improve bonding force of a silicon layer attached to the base substrate.
Further, methods in which an SOI substrate is manufactured by attaching a silicon layer, which has been separated from a silicon wafer, to a glass substrate are known (see Reference 1: Japanese Published Patent Application No. Hei11-163363, Reference 2: Japanese Published Patent Application No. 2004-087606, and Reference 3: Japanese Published Patent Application No. 2005-252244).